My lecturer uses powerpoints as a teaching material. During the first class she told me that we are using a book as resource for our class. But one day I realised that some parts are not from the book. So the question is: should she provide the reference she use? IMO, she should tell us what she is basing her teaching on.

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    Can you clarify whether your primary concern is about ethics/plagiarism or about being able to refer to the original sources to facilitate your learning?
    – Ben Bolker
    Commented Dec 6, 2020 at 21:29
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    It is not, in general, necessary for the lecturer to use a reference in preparing lectures. Commented Dec 6, 2020 at 23:13
  • Are you worried that if she's teaching stuff not in any book, that it might be incorrect? Commented Dec 7, 2020 at 0:40
  • @OwenReynolds If somebody has been teaching a course like Calculus 1 for twenty years, first they don't need a book as a reference, and second the chance that they include something that is incorrect without using a book is no more likely than that they copied a typo from a book.
    – alephzero
    Commented Dec 7, 2020 at 0:55
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    @alephzero: Owen's comment doesn't imply that such a worry is justified. I assume the comment is just trying to identify the source of OP's confusion (i.e. why they're asking) so that answers can actually address that concern. (Likewise, Ben's comment asks about OP's primary concern in order to judge whether this question is a duplicate of the one cag51 linked or not.)
    – V2Blast
    Commented Dec 7, 2020 at 1:56

2 Answers 2


As with writing, anything presented in a class without citation should be either the work of the presenter or common knowledge. Your teachers are supposedly experts in the fields they teach, and so should have amassed quite a lot of the common knowledge in their fields. For example, I'd happily describe the Bell-LaPadula model and its applications, mentioning Bell and LaPadula by naming the model, but without further citation.

For those courses I taught that had a textbook, I organized classes around the textbook, but certainly presented material not contained therein, often without citation, because, as Buffy has written in another answer, "It is known, even if not known to you and the other students."

If I had used only the textbook publisher's slides, I'd have felt I was cheating my students. If a student had asked me the source of material in the lectures but not in the textbook, I'd have said, "Right out of my head unless specifically cited." I expect your professor might answer the same way.

If the textbook were sufficient, professors could announce it on the first class, then say, "I'll see you in three months for the final exam." The role of the professor is to explain, elaborate, and expand. The latter two necessarily go beyond the content of the textbook.

With all of that said, I'm not sure I understand the goal of your question. Do you believe there's a "secret source" that's somehow being hidden from you? I doubt it. More likely, there are many sources, accreted over years of study by the professor.

If you're looking for material to supplement the textbook, ask. Professors want you to learn and if there are accessible supplemental resources, they should tell students about them.

  • Actually I take a bit issue with extending 'common knowledge' because usually anything taught in university is not 'common knowledge' in the sense like anybody with a high-school degree would know. I am not trying to pick words, but I think it is important to define this properly. Also the other way saying 'any expert in the field would know' then I wouldnt even have to put in citations in my research papers, because, honestly the stuff cited should be common knowledge to the expert. Where is the line?
    – lalala
    Commented Dec 7, 2020 at 7:21
  • @lalala Every discipline has its own body of common knowledge. I, as a computer scientist, have a different body of common knowledge than my friend the virologist, and I doubt that the high school graduate knows very much of either. The definition I learned in high school was that something is common knowledge if one can find the same information in three different resources. Consider again what I quoted from Buffy's answer: "It is known, even if not known to you and the other students."
    – Bob Brown
    Commented Dec 7, 2020 at 12:37

For a few reasons, a lecturer should let students know the source of their teaching materials. But not everyone will and some might actually have reasons not to if they are trying to guide students toward some things but away from others. That should be rare, I think.

But the issue can be a bit subtle. Is the use of materials intended for teaching without citation a form of plagiarism? Is it a form of improper "publishing"? People will answer differently.

Plagiarism is about ideas, not their explicit expression. If the instructor is teaching well known things (common knowledge) then there is no implication that the things taught are the ideas of the instructor. Hence it is hard to claim it is plagiarism. It is known, even if not known to you and the other students.

Publishing the work of others without citation is an offense, but against copyright. But is teaching a form of "publishing"? And is there an implicit license for teaching materials to be used in teaching? It isn't always obvious.

So, I find the legal and moral issues a bit cloudy and would, therefore, defer on those issues to faculty in most cases. Not all. Most. But since the issues are (IMO) on the borderline, it is probably better to cite them than not to cite them unless there is some firm reason not to.

But, there is an educational reason for making the source(s) of materials available to students. Especially conscientious students will, perhaps, occasionally, want to follow up with those sources and thus enhance their educations. I applaud that when it can be made to happen.

But there is an action item here. You can, perhaps, ask her for her sources. I suspect that you will likely get them. If she refuses, you can validly ask why. But to save yourself from some grief, ask in a non-confrontational way. Perhaps she is happy to share them. In fact, if you have already been given a list of resources for the class, as some instructors provide, you might even find the materials there.

And, of course, some slides and such are produced by the instructor herself, based on her knowledge, though it may be common knowledge, the source of which she has long forgotten.

For some materials used in advanced courses, there is probably a stronger case to be made that not citing them is a violation of plagiarism standards, copyright, or both. I've assumed above that this is not the situation here.

  • Yup truly agreed, just hope that she would tell me about it as the first class she states that all are from the same book
    – no name
    Commented Dec 6, 2020 at 14:44
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    Normally one can assume that the bulk of the material comes from the books announced at the beginning of the course. In my case, it's quite unrecognizable, because I rearranged and -adapted the material according to my preferences, and spicing them up with self-made animations and the like, but all the books are mentioned at the beginning of the class. I doubt it makes sense to repeat that in every slide or lecture. Commented Dec 6, 2020 at 15:08
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    also, instructors are human: especially if they have been using these slides for a while, they may have started out being entirely based on the book, but gradually moved away as the instructor modified the content based on their own knowledge
    – Ben Bolker
    Commented Dec 6, 2020 at 21:31

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